This invention was made with government support under grant CA 09441 awarded by the National Cancer Institute. The government of the United States has certain rights in this invention.
This invention relates to boron analogs of amino acids and small peptides and the use of the analogs to inhibit growth or colony formation of mammalian cells.
Three major families of antitumor agents are known. Each of the families of agents is associated with a recognized mechanism of action. The families of antitumor agents and associated mechanisms may be defined as follows: First, antitumor agents may be alkylating agents, which generally bind in a covalent manner with DNA to form bifunctional lesions. The bifunctional lesions involve adjacent or nearby bases on the same strand, or alteratively involve bases on opposite strands forming interstrand crosslinks. Second, antitumor agents may be antimetabolites, which generally inhibit enzymes involved in the synthesis or assembly of DNA. Alternatively, an antimetabolite may serve as a fraudulent or analog substrate of DNA processes. Third, antitumor agents may be antibiotics, which work by intercalating into the DNA helix or introducing strand breaks into DNA.
Thousands of potential anticancer agents have been evaluated. Essentially all effective agents (of which very few have been found) appear to work by one of the above-mentioned mechanisms. The subject invention concerns a class of molecules which are not associated with any of the three major families of antitumor agents.
Proteases and protease inhibitors have been reported in association with cancer-related processes. The most common associations involve increased protease enzyme activities or enzyme concentration. Such increased protease activity may be associated with transformation of cells by viruses, chemicals or other agents, as well as with the metastatic potential of cancer cells. Additionally, data have been published which suggest that protease inhibitors may prevent or reduce the incidence of transformation and reduce the metastatic potential of cancer cells. A number of protease inhibitors has been previously evaluated against murine tumor cells in both culture and in whole animals as potential antitumor agents. Most are inert or require very high concentrations to achieve significant tumor cell killing.
The synthesis and protease inhibition properties of Cbz-ala-borovaline and Cbz-ala-borophenylalanine (trivialized names) have been previously reported (Kinder and Katzenellenbogen, J. Med. Chem. 28:1917-25, 1985). One of the analogs, Cbz-ala- borophenylalanine, has also been evaluated for cytotoxicity against Lewis lung murine tumor cells in culture (Goz et al., Biochem. Pharmacol. VOL/PAGE 1986). The Kinder paper contains no data relating to the potential antitumor activity of these molecules, and the Goz paper found only modest activity against a murine tumor line. Other protease inhibitors have been evaluated in vitro and in vivo as antitumor agents, always with disappointing results.